Method of manufacturing a die for extruding honeycomb body

ABSTRACT

Disclosed herein is a die for extruding honeycomb structural body, which comprises a die base body made of an alloy steel and a plate of a wear resistant alloy which is joined to the front face side of the die base body. In the wear resistant alloy plate are formed forming slits having a sectional profile conforming to that of a honeycomb structural body to be shaped and having a given depth from the front face of the die toward the rear face thereof, and a plurality of openings are formed independently of each other in the die base body from the rear face of the die toward the front face thereof to communicate with the forming slits. The wear resistant alloy plate may be joined to the die base body through an alloy steel plate having the same as or thinner than the thickness of the wear resistant alloy plate. A method of manufacturing such a honeycomb structural body-extruding die is also disclosed.

This is a division of application Ser. No. 664,003, filed Oct. 23, 1984,now U.S. Pat. No. 4,653,996.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a die for extruding a honeycombstructural body (hereinafter referred to as "honeycomb forming die") anda method of manufacturing the same, and more particularly, the inventionrelates to a honeycomb forming die used to extrude a plasticizedmaterial to form a honeycomb structural body in which a plate made of awear resistant alloy (for instance, hard metal) is joined to the diefront face portion to which forming slits are to be formed, and theforming slits are formed in the wear resistant alloy plate. Theinvention also relates to a method of manufacturing the same.

(2) Description of the Prior Art

Heretofore, there has been known a honeycomb forming die as shown inFIG. 1 (FIG. 1a is a plane view of the honeycomb forming die, and FIG.1b is a sectional side view of the forming die shown in FIG. 1a asviewed from an arrow A-A'). More particularly, the honeycomb forming dieshown in FIG. 1 is a so-called integral structure in which honeycombforming slits 3 (hereinafter referred to as forming slits) having aspecified depth are formed from the die front face 1 toward the die rearface 2 in such a sectional profile as to conform to the sectionalprofile of a honeycomb structural body to be shaped (a rectangularsection honeycomb in the forming die shown in FIG. 1), and a pluralityof openings 4 are independently formed from the die rear face 2 towardthe die front face 1 to communicate with the above forming slits 3.

The honeycomb forming die shown in FIG. 1 is generally produced asfollows:

That is, a block body is prepared from a metallic material by means of ageneral purpose machine tool such as lathe or the like, and numerousindependent openings 4 are bored from one of the faces (die rear face 2)of the block body toward the other face (die front face 1) of the blockbody by means of a drilling machine. Thereafter, the honeycomb formingslits 3 are worked from the die front face 1 toward the die rear face 2of the block body, for instance, by electrical discharge machining orthe like to communicate with the openings 4.

When the honeycomb structural body is shaped by using the honeycombforming die thus produced, a raw material of the honeycomb structuralbody to be shaped, such as a plasticized material of ceramic, is pressfed into all the openings 4 and the plasticized material thus press fedflows into the forming slits while being squeezed, whereby the ceramichoneycomb structural body is continuously extruded from the formingslits 3.

However, when the honeycomb structural body is extruded by using such aconventional honeycomb forming die, the forming slits 3 are worn by theplasticized material passing through the forming slits 3, so that thewidth of the slits becomes larger. Consequently, in order to assure thedimensional precision of the honeycomb structural bodies, there is aproblem that exchange of expensive dies must be made at a number oftimes. Particularly, when the honeycomb structural bodies are shaped byusing a raw material of alumina or silicon carbide, a raw material ofmullite having a coarse particle size or the like, the wear of theforming slits 3 is conspicuous, so that the durable life of the diebecomes remarkably shorter.

Further, according to the conventional honeycomb forming die, thedimensional variations in the forming slits causes the difference in theextruding rate of the material to be extruded over the forming slits, sothat there are problems that cracks are formed in the honeycombstructural body extruded thereby in a firing process, or the material isnot extruded into a honeycomb shape.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a die for extrudinga honeycomb structural body (hereinafter referred to as a honeycombforming die) which eliminates the above-mentioned problems.

More specifically, the object of the present invention is to provide ahoneycomb forming die in which the wear resistance of forming slits isincreased to prolong the durable life of the forming die.

It is another object of the present invention to provide a method ofmanufacturing such a honeycomb forming die.

It is still another object of the present invention to provide ahoneycomb forming die which prevents an unreasonable thermal stressconcentration in the forming die while enhancing the wear resistancethereof.

It is a further object of the present invention to provide a method ofmanufacturing such a honeycomb forming die in which the thermal stressconcentration is prevented.

According to a first aspect of the invention, there is a provision of ahoneycomb forming die comprising a die base body made of an alloy steeland a plate of a wear resistant alloy which is joined to the front faceside of the die base body, wherein the wear resistant alloy plateincludes forming slits having a sectional profile conforming to that ofa honeycomb structural body to be shaped and having a given depth fromthe front face of the die toward the rear face thereof, and a pluralityof openings are formed independently of one another in the die base bodyfrom the rear face of the die toward the front face thereof tocommunicate with the forming slits.

According to a second aspect of the invention, there is a provision of amethod of manufacturing a honeycomb forming die provided with formingslits having a sectional profile conforming to that of a honeycombstructural body to be shaped and a given depth from the front face ofthe die toward the rear face thereof and a plurality of openings formedfrom the rear face of the die toward the front face thereof tocommunicate with the forming slits, which method comprises the steps ofworking a plate made of a wear resistant alloy and constituting the diefront face and a die base body made of an alloy steel and constitutingthe die rear face, into given profiles; flame-spraying the wearresistant alloy onto one of the worked faces of the die base body toform a flame-sprayed layer of the wear resistant alloy; joining the wearresistant alloy plate to the die base body through the flame-sprayedlayer of the wear resistant alloy; working the forming slits in the wearresistant alloy plate; and boring the openings in the die base body.

According to a third aspect of the present invention, there is aprovision of a honeycomb forming die in which a wear resistant alloyplate is joined to a flame-sprayed layer of the wear resistant alloywhich is formed on one face of a plate of alloy steel having a thicknesswhich is the same as or less than the thickness of the wear resistantalloy plate, a die base body is joined to the other face of the alloysteel, a plurality of independent holes are formed from the die basebody toward the alloy steel plate, and the forming slits are formed fromthe wear resistant alloy plate toward the alloy steel plate tocommunicate with the forming slits, whereby the warping or peeling-offof the wear resistant alloy plate is prevented to prolong the durablelife of the honeycomb forming die.

According to a fourth aspect of the present invention, there is aprovision of a method of manufacturing a honeycomb forming die providedwith forming slits having a sectional profile conforming to that ofhoneycomb structural body to be shaped and a given depth from the frontface of the die toward the rear face thereof and a plurality of openingsformed from the rear face of the die toward the front face thereof tocommunicate with the forming slits, which method comprises steps ofworking a plate made of a wear resistant alloy plate constituting thefront face of the die, a die base body made of an alloy steel andconstituting the rear face of the die, and an alloy steel plateinterposed between the wear resistant alloy plate and the die base bodyinto given profiles; flame-spraying a metal having substantially thesame properties as those of the wear resistant alloy plate to form aflame-sprayed layer of the wear resistant alloy onto; grinding the planeof the wear resistant alloy flame-sprayed layer to a given thickness andjoining the wear resistant alloy plate on the wear resistant alloyflame-sprayed layer; joining ther alloy steel plate to which the wearresistant alloy plate is joined, to the die base body; working theforming slits from the wear resistant alloy plate toward the alloy steelplate; and boring the openings from the die base body toward the alloysteel plate.

These and other objects, features, and advantages of the presentinvention will be well appreciated upon reading of the followingdescription of the invention when taken in conjunction with the attacheddrawings with understanding that some modifications, variations andchanges thereof could be easily made by the skilled in the art, to whichthe invention pertains, without departing from the spirit of theinvention and scope of claims appended hereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a plane view of a conventional honeycomb forming die;

FIG. 1b is a sectional side view of the honeycomb forming die in FIG. 1aas viewed from an arrow A-A';

FIG. 2 is a sectional side view illustrating the construction of anembodiment of a honeycomb forming die according to the presentinvention;

FIG. 3 is a sectional side view of another embodiment of the honeycombforming die according to the present invention;

FIG. 4 is a schematic view illustrating a method of manufacturing thehoneycomb forming die shown in FIG. 2; and

FIG. 5 is a schematic view illustrating a method of manufacturing thehoneycomb forming die shown in FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be explained in more detail with reference tothe preferred embodiments thereof with reference to the attacheddrawings, which are merely illustrative of the invention, and should notbe interpreted limiting the scope of the invention.

The same and similar reference numerals represent the same or similarparts throughout the drawings.

In the drawings, a reference numeral 5 is a hard metal plate, referencenumerals 6 and 6' die base body, a reference numeral 7 a first joiningportion which is formed by flame-spraying a powder of a hard metal suchas tungsten-carbon series, a reference numeral 7' a flame-sprayed layer,a reference numeral 8 a plate of an alloy steel, a reference numeral 9 asecond joining portion at which the alloy steel plate 8 is joined to thedie base body 6' by means of, for instance, brazing or the like.

Before entering the detailed explanation of the honeycomb forming dieand a manufacturing method thereof according to the present invention,the difference between the conventional embodiment shown in FIG. 1 andthe present invention will be briefly explained. That is, a plane viewof each embodiment according to the present invention which will now beexplained is the same as that of FIG. 1a provided that the squareportion divided by the forming slits 3 of FIG. 1a is the hard metalplate 5.

The embodiment shown in FIG. 2 is constituted by joining the hard metalplate 5 and the die base body 6 made of the alloy steel together at thefirst joining portion 7 (the joining way will be described later withreference to FIG. 4). The die base body 6 used in this embodiment ispreferably made of an alloy steel such as invar, which has substantaillythe same thermal expansion coefficient as that of the hard metal plate5. The forming slits 3 are formed from the hard metal plate 5 toward thedie base plate 6, that is, the die front face 1 toward the die rear face2, and a plurality of independent openings 4 which communicate with theforming slits 3 are bored from the die base body 6 toward the hard metalplate 5, that is, from the die rear face 2 toward the die front face 1(a method of manufacturing the embodiment shown in FIG. 2 will bedescribed later).

An embodiment according to the present invention shown in FIG. 3, isprovided with the hard metal plate 5 the alloy steel plate 8, the diebase body 6; and the hard metal plate 5 and the alloy steel plate 8 arejoined via the first joining portion 7 in the same manner as in theembodiment shown in FIG. 2. On the other hand, the alloy steel plate 8and the die base body 6' are joined together via the second joiningportion 9 (the joining method will be described later in connection withFIG. 5). Forming slits 3 are formed from the hard metal plate 5, namelythe front face 1 of the die toward the alloy steel plate 8, and theplurality of the independent openings which communicate with the formingslits 3 are formed from the die base body 6', that is, the rear face 2of the die toward the alloy steel plate 8 (a method of manufacturing theembodiment shown in FIG. 3 will be described later in connection withFIG. 5.)

Since the forming slits 3 are formed in the hard metal plate 5 in theabove-described embodiments shown in FIGS. 2 and 3, the wear resistanceof the forming slits 3 in the extrusion molding is increased. When thehard metal plate 5 is directly joined to the die base body 6, as in theembodiment shown in FIG. 2, the joining is effected at a hightemperature according to the liquid phase diffusion welding method.Accordingly, if there is any difference in thermal expansion between thehard metal and the alloy steel constituting the die base body 6, thereis a likelihood that a bimetal phenomenon brings about warpage of thehard metal plate 5 of production of voids at the joining portion, sothat the hard metal plate 5 is peeled off from the joining portion afterthe formation of the forming slits 3. In the embodiment illustrated inFIG. 3, the hard metal plate 5 is prevented from being warped or peeledoff by joining the hard metal plate 5 to the die base body 6' via thealloy steel plate 8 with the use of the ordinary alloy steel.

Next, the method of producing the embodiment shown in FIG. 2 will beexplained with reference to FIG. 4.

(a) As shown in FIG. 4a, an alloy steel such as invar is first processedby means of a general purpose machine tool such as a lathe to shape adie base body 6.

(b) Next, as shown in FIG. 4b, a powder of the hard metal (which is thesame material as that of the hard metal plate mentioned later) isflame-sprayed onto the die base body at one face thereof to form theflame-sprayed layer 7' at a given thickness (for instance, 0.5-3.0 mm).

(c) Further, as shown in FIG. 4c, the surface of the flame-sprayed layeris ground to form the first joining portion 7 uniformly having a giventhickness (for instance 0.3 to 1.0 mm).

(d) Then, as shown in FIG. 4d, a copper sheet (not shown) is interposedbetween the hard metal plate 5 shaped at a specified thickness (forinstance, about 5 mm) and in a specified profile and the above firstjoining portion 7, and the liquid phase diffusion welding is carried outat a temperature of about 1,000° C. to perform the joining between theabove hard metal plate 5 and the die base body 6.

(e) Thereafter, as shwon in FIG. 4e, a plurality of the openings 4 arebored in die base body 6 from the rear face 2 of the die by means of,for instance, a drilling machine. This boring may be performed after theabove step (c).

(f) As shown in FIG. 4f, the forming slits 3 are formed from the surfaceof the above hard metal plate 5, that is, the front face 1 of the die bymeans of the electrical discharge machining or metal machining tocommunicate with the above openings 4. The forming slits are preferablyformed extending over the joining portion 7 to reduce the pressureapplied to the joining portion.

The die according to the embodiment shown in FIG. 2 for forminghoneycomb structural bodies may be produced by the above-mentioned steps(a)-(f). In the embodiment illustrated in FIG. 2, although explanationhas been made on the case where the hard metal plate 5 is joined to thedie base body 5 through the first joining portion 7 (the above step(d)), when invar is used as the die base body 6, the hard metal 5 may bedirectly joined to the die base body 6 through the above-mentionedliquid phase diffusion welding.

Next, the method of producing the embodiment shown in FIG. 3 will bedescribed in connection with FIG. 5.

(a') As shown in FIG. 5a', a plurality of the plates 8 of an alloy steelsuch as carbon steel are worked to have a given thickness (for instance,about 10 mm) and a given size (intergral times as large as the pitchdimension of the slit width of the forming slits 3 mentioned later). Thesize of the alloy steel plate 8 is preferably designed to be smallerthan about 50 mm×50 mm so that the adverse influence due to thedifference in the thermal expansion between the hard metal and the alloysteel may be avoided.

(b') Next, the flame-sprayed layer 7' is formed in the same manner as inthe above step (b) (shown in FIG. 5b').

(c') Then, surface-grinding is performed in the same manner as in theabove step (c) to form a first joining portion 7 (shown in FIG. 5c').

(d') Next, as shown in FIG. 5d', surface-grinding is performed to makethe thickness of the alloy steel plate 8 to be, for instance, in a rangeof 1 mm to 5 mm. Needless to say, the surface grinding is carried outsuch that the surface of the above flame-sprayed layer 7 is parallel tothat of the alloy steel 8.

(e') Then, as shown in FIG. 5e', the hard metal plate 5, worked to havea given thickness (for instance, about 5 mm) and the same size as thatof the alloy steel plate 8, is diffusion-welded to the alloy steel plate8 in the same manner as in the above step (d).

(f') Thereafter, as shown in FIG. 5f', the plurality of alloy steelplates 8 each having the above hard metal plate 5 joined thereto arejoined to the die base body 6' (for instance, made of the alloy steelsuch as tool steel) worked in a specified shape, by brazing such thatthe side faces of the alloy steel plates 8 to which the hard metalplates are joined are adhered to one another (the joining portion isshown as the second joining portion 9). It is preferable that thejoining temperature is set at a temperature far lower than theabove-mentioned diffusion welding temperature so that no strain is causeupon the first joining portion 7 by thermal stress. Therefore, thejoining in the step (f') may be performed by soldering or brazing. Theabove joining may be performed by a mechanical means such as screwfixing (not shown) or the like.

(g') Then, as shown in FIG. 5g', a plurality of the openings 4 are boredfrom the rear face 2 of the above die base body 6' toward the alloysteel plate 8 by means of a drilling machine or the like. The boringlocations of the openings 4 are selected such that the centers of theopenings may be in coincidence with those of the forming slits mentionedlater.

(h') As shown in FIG. 5h', the forming slits 3, which communicate withthe above openings 4, are bored from the surface of the above hard metalplate 5, that is, the die front face 1 toward the alloy steel plate 8,by electrical discharge machining or metal machining. The locations ofsome of the above forming slits 3 are selected to be in coincidence withthe place where the hard metal plate 5 and the alloy steel plate 8 arejoined with the adjacent ones. The depth of the forming slits ispreferably deeper than that of the joining portion 7 so that theextruding force applied to the first joining section 7 may be decreasedthereby.

The die according to the embodiment of the present invention, as shownin FIG. 3, for shaping the honeycomb structural body can be producedaccording to the steps (a')-(h').

In the above, the honeycomb structural body and the method of producingthe same have been described in detail, but the invention is not limitedthereto. The invention may be:

(1) The hard metal plate 5, in which the forming slits 3 are formed, maybe made of other wear resistant alloy. In such a case, it is preferablythat the first joining portion 7 may be a flame-sprayed layer made of analloy powder having substantially the same properties as those of thewear resistant alloy used.

(2) Although the openings 4 are bored before the forming slits 3 areworked, the openings may be bored after the forming slits are formed.

(3) Although explanation has been made on the case where the sectionalprofile of the forming slits 3 is square, they may be triangular,hexagonal, octagonal or rectangular depending upon the intendedhoneycomb profile.

(4) The extrusion material in the forming die according to the presentinvention is not limited to the ceramic material, and as a matter ofcourse, the invention may be applied to a rubber material.

As mentioned above, the present invention can provide the honeycombforming die and the producing method thereof by which the followingeffects can be produced. That is,

(i) As compared with the dies of the conventional structure, the wearamount of the forming slits is lower and the durable life of the die canbe more prolonged than that of the conventional dies (for instance, byabout 10 times as long as that of the conventional dies). In the casethat a hard raw material of alumina or SiC material and mullite materialwith a coarse particle size is extruded, the variation of the slit widthis smaller than the conventional dies, and therefore, the durable lifeduring which the die can be used for production purpose is increased.

(ii) Since variation in the slit width of the honeycomb structural bodyextruded is smaller, the forming die is permits excellent dimensionalprecision for extruding the honeycomb structural body for a long periodof time.

(iii) Since the dimensional precision is good, as mentioned above, novariations in the material density at various portions of the core ofthe honeycomb structural body thus extruded occurs. For instance, in thecase of the ceramic honeycomb, cracking of the shaped article can beprevented during the firing process.

What is claimed is:
 1. A method of manufacturing a honeycomb structuralbody-extruding die provided with forming slits having a sectionalprofile conforming to that of honeycomb structural body to be shaped anda given depth from the front face of the die toward the rear facethereof and a plurality of openings formed from the rear face of the dietoward the front face thereof to communicate with the forming slits,which method comprises steps of working a plate made of a wear resistantalloy and constituting the die front face and a die base body made of analloy steel and constituting the die rear face into given profiles;flame-spraying a wear resistant alloy onto one of the worked faces ofthe die base body to form a flame-sprayed layer of the wear resistantalloy, joining the wear resistant alloy plate to the die base bodythrough the flame-sprayed layer of the wear resistant alloy; working theforming slits in the wear resistant alloy plate; and boring the openingsin the die base body.
 2. A method of manufacturing a honeycombstructural body-extruding die provided with forming slits having asectional profile conforming to that of honeycomb structural body to beshaped and a given depth from the front face of the die toward the rearface thereof and a plurality of openings formed from the rear face ofthe die toward the front face thereof to communicate with the formingslits, which method comprises steps of working a plate made of a wearresistant alloy plate constituting the front face of the die, a die basebody made of an alloy steel and constituting the rear face of the die,and an alloy steel plate to be interposed between the wear resistantalloy plate and the die base body into given profiles; flame-spraying ona face of the alloy steel plate a metal having substantially the sameproperties as those of the wear resistant alloy plate to form aflame-sprayed layer of the wear resistant alloy; grinding the plane ofthe wear resistant alloy flame sprayed layer up to a given thickness andjoining the wear resistant alloy plate to the wear resistant alloyflame-sprayed layer on the alloy steel plate; joining the other face ofthe alloy steel plate opposite to the one face, which the wear resistantalloy plate is joined, to the die base body; working the forming slitsfrom the wear resistant alloy plate toward the alloy steel plate; andboring the openings from the die base body toward the alloy plate.